Quadrupole mass spectrometers are commonly used to perform mass analysis. These spectrometers, when used in a resolving mode, employ 4 rods which are usually relatively lengthy (e.g., 20 cm) and which are both made and assembled with extreme precision. When used in a resolving mode they are pumped to a relatively high vacuum (e.g. 10.sup.-5 Torr) and both RF and DC voltages are applied to them. While the RF and DC voltages can vary depending on the frequency of operation and the mass range, typical values for the RF are of the order of 1600 volts peak-to-peak at 1 MHz, and for the DC typically .+-.272 volts peak-to-peak. (These values are typical for a mass range of 600 Daltons and an inscribed radius r.sub.0 for the rod set of 0.415 cm.) The costs of such mass spectrometers, including their associated power supplies and vacuum pumps, are usually extremely high.
There has for many years existed a need for a simpler less expensive mass spectrometer, and numerous attempts have been made to fill this need. However while the costs have been reduced, quadrupole and other rod mass spectrometers (e.g., octopoles and hexapoles) have continued to remain extremely expensive and to require very close tolerances and high vacuum pumping equipment, as well as costly power supplies.